I. Field of the Invention
This invention relates generally to orthodontic appliances, and more specifically to a new article of manufacture useful in the correction of maloccluded teeth.
II. Discussion of the Prior Art
In the correction of alignment, positioning and malocclusion of teeth, various mechanical arrangements are used for applying steady forces to the teeth over a prolonged period of time such that the teeth are urged into an aligned disposition within the oral cavity. Typically, bands or brackets are fastened to certain teeth and then a wire arrangement, referred to as an arch wire, is fastened to the bands with the arch serving to apply forces in appropriate directions so as to urge the affected teeth into a different positional orientation. The arch wire is commonly drawn from stainless steel and it is important that it possess properties of flexibility so that it can be bent into a desired shape while, at the same time, exhibiting sufficient stiffness and resiliency (inherent memory property) such that desired forces are imparted upon the teeth to be repositioned.
In the past, orthodontists have primarily employed strands of stainless steel wires having either a circular or square cross-section in fabricating orthodontic arches. While stainless steel wires of a given diameter, i.e., typically in the range of 0.016 to 0.022 inches are commonly employed, they suffer from a lack of flexibility because that outside diameter is necessary to ensure that the wire will have the requisite resiliency to provide the desired forces upon the teeth. While reducing the diameter may render the wire more flexible, its resiliency is correspondingly reduced such that the wire is subject to permanent deformation and/or breakage. More recently, an arch wire formed from a nickel-titanium alloy and sold under the trademark, Nitinol Activ-Arch, by the Unitek Corporation of Monrovia, California, has been introduced which possesses the desirable characteristics of reduced stiffness (greater flexibility) and high resistance to deformation as compared to stainless steel of comparable dimensions. The use of arch wires of Nitinol alloy in orthodontia is described in the Andreason U.S. Pat. No. 4,037,324.
In addition, orthodontic work is frequently performed on patients who may be somewhat self-conscious over their appearance and are, at times, embarrassed by the presence of the orthodontic appliances on their teeth. Stainless steel wires of a requisite diameter tend to be somewhat unsightly. The Chasanoff U.S. Pat. No. 4,050,156 suggests coating a stainless arch wire with a plastic matrix in which a suitable colorant is intermixed so as to match the natural tooth color of the patient. Here, however, the plastic material is not used as a structural member as in the present invention, but is only used as a method of applying a colorant to a stainless steel surface.